This study is designed to investigate our observation that the diurnal rhythm of blood pressure is different in two groups of black hypertensive patients studied under a common protocol at two medical centers in New York City (New York Hospital-Cornell and Harlem Hospital), separated geographically by only a few miles, but serving very different populations. Harlem hypertensive had a diminished nocturnal fall of blood pressure (' a 'non-dipping' pattern). The blood pressure pattern did not differ in two corresponding groups of normotensives. Harlem hypertensives had lower socioeconomic status than the other 3 groups. The major objective of the study is to test the hypothesis that the difference seen in the hypertensives is the result of psychosocial factors, including socioeconomic status, occupational stress, and domestic stress, acting via (a) effects on BP during the day, and/or (b) effects on sleep and BP during the night. 600 normotensive and hypertensive black and white subjects will be studied at the two institutions with a common protocol. This will include a 24 hour blood pressure and activity recording, split (day and night) 24 hour urine collection for cortisol, catecholamines, etc., and home polysomnography. Questionnaires will evaluate psychosocial and demographic factors, and target organ damage will be assessed by echocardiography, digitized electrocardiography, ankle arm index, and micro-albuminuria. The possible effects of neighborhood environments on blood pressure patterns will also be evaluated. It has been suggested that the non-dipping pattern commonly seen in black hypertensive patens may adversely affect their prognosis, and we will related the blood pressure patterns to the different measures of target organ damage in the heart and kidneys.